1. Field of the Invention
This invention relates to optical-electronic integrated circuits, and more specifically to a monolithic integration of an optical-electronic integrated circuit including a laser, a photodetector and a heterojunction bipolar transistor and to a process for fabricating such a monolithic integrated circuit.
2. Description of Related Art
Light-emitting diodes, semiconductor injection lasers, photodetectors and photodiodes are devices which are assembled to create an optical-electrical communication system. The usefulness of such a system is largely determined by its operating speed. Within an optical-electrical communication system, optical signals are detected and converted to electrical signals, the electrical signals are conveyed to a light emitting diode or laser, generating optical signals which are communicated to optical signal detectors. One factor in realizing a high operating speed is a reduction in the time expended communicating signals between optical signal detectors and optical signal generators.
Device parasitics are a major limitation to the ultimate operating speeds of lasers and photodetectors. Thus, another factor in realizing a high operating speed is a capability to reduce device parasitics and the junction capacitances and internal resistances that cause large parasitics.